Effect of Digestion Methods on Quantitative Analysis of Heavy Metal Elements

In order to investigate the effects of three digestion methods(platen heating digestion,high pressure closed-vessel digestion and microwave digestion) on analysis of Cr,Cu,Zn,Cd and Pb in the digestion,Cr,Cu,Zn,Cd and Pb in the digestons of the national standard reference material(GBW07440) digested respectively with three methods above were analyzed by ICP-MS under its optimized model to establish a best method for determining and analyzing a variety of heavy metals in soil.The results suggested that microwave digestion was a most complete method and its digestion solution was most clarifying,but the residue by platen heating digestion and pressure close-vessel digestion remained more than microwave digestion.Detection limits of three methods were up to level of μg/L or lower level.However,the level of microwave digestion was lowest.Correlative coefficient of the calibration curves was over 0.999 90 by using ICP-MS determination of five types of elements.Maximum RSD of Cr,Cd and Pb was lower than that of Cu and Zn.The sensitivity and accuracy of ICP-MS were satisfied.Basically,testing value of three methods brought into correspondence with standard value in certified reference material.In conclusion,the method of microwave digestion was more first recommended to digest soil heavy metals.